The present invention relates to a brake disc for disc brakes wherein at least one friction surface includes at least one groove.
Brake discs of this type are known in the art. The grooves cut into the friction surfaces of the brake discs are used to improve cooling of the brake disc by increasing the cooling surface and by better turbulences of the cooling air, on the one hand. On the other hand, the grooves are used to improve response of the brake when the brake disc is wet because water disposed on the brake disc can be taken up in the grooves. Another advantage of the grooves is that they permit being used as a wear indicator. German patent application No. 40 02 695 discloses a brake disc of this type with decoratively arranged grooves in the friction surfaces. When the brake disc has worn by an amount which corresponds to the depth of the grooves, the grooves will disappear. This permits a simple visual check from outside. As soon as the grooves are not visible any longer, the worn brake disc must be replaced.
However, the prior art brake discs suffer from the disadvantage that the structures of the grooves can only be made in a costly operation. A brake disc blank is generally machined in such a fashion that initially the friction surfaces are smoothed in a first processing machine. Subsequently, the brake disc must be removed from the first processing machine and clamped into a milling machine in a second step for cutting the grooves. With the rigid brake disc non-rotating, the grooves are then milled in by the milling machine. The miller is required to perform -a complicated two-dimensional movement.
An object of the present invention is to provide an improved brake disc for disc brakes and to permit brake disc manufacture to be reduced in costs especially as far as the application of the grooves is concerned.